It has been the general practice to provide moisture control characteristics in the foot of a sock by knitting both hydrophobic and hydrophilic yarns in plated relationship throughout the foot and with the hydrophobic yarn plated on the inside of the foot while the hydrophilic yarn is plated on the outside of the sock so that moisture generated by the foot of the wearer is wicked and transported outwardly away from the foot by the hydrophobic yarn and is absorbed and evaporated from the sock by the hydrophilic yarn. Since the shoe covers at least a major portion of the foot of the sock, the wicking of the moisture from the inner surface to the outer surface of the foot of the sock and evaporation of the moisture from the outer surface is not very efficient, particularly when a great amount of moisture is generated by the foot of the wearer when engaging in athletic activities.
U.S. Pat. No. 4,898,007 discloses a moisture management sock in which the heel and toe portions of the foot are knit predominately, or entirely, of hydrophilic yarn while the middle portion of the foot extending therebetween is knit of hydrophobic yarn. According to this patent, moisture absorbed from the wearer's foot by the hydrophilic yarn in the toe and heel portions is transferred by wicking action into the hydrophobic yarn in the medial portion of the foot to be evaporated therefrom. Thus, the foot of the sock is divided into a first zone at the toe of the sock which is knit predominately of hydrophilic yarn, a second zone at the heel of the sock which is also knit predominately of hydrophilic yarn, and a third zone extending between the heel and toe which is knit predominately of hydrophobic yarn. The first toe zone and the second heel zone are joined to the third medial or instep zone along juncture lines extending in a coursewise direction. This type of moisture management sock may not provide sufficient evaporation of the moisture generated by the foot of the wearer, particularly when the sock is used during athletic activities and a great amount of moisture is generated by the foot of the wearer.
It is also known to knit "splitfoot" socks in which the lower half or sole of the foot is knit of a yarn of one color, usually white, while the upper half or instep of the foot is knit of another color of yarn. U.S. Pat. No. 721,190 discloses an example of this type of "splitfoot" sock in which the yarn forming the lower half or sole of the foot is knit in partial courses of one yarn with free cut ends at opposite sides thereof, where the sole joins the instep. The instep is knit in partial courses of another yarn with free out ends with the partial courses of the sole yarn. The partial courses of the instep yarn overlap the partial courses of the sole yarn in a pair of common wales at the juncture of the sole and instep. This formation of wales of plated stitch loops formed of both the instep and sole yarns extending along opposite sides of the foot of the sock forms a heavy ridge or thickened fabric area therealong.